startingstrengthmirrorfandomcom-20200214-history
Pectoralis major muscle
The Pectoralis major (popularly known as pecs) is a thick, fan-shaped muscle, situated at the upper front (anterior) of the chest wall. It makes up the bulk of the chest muscles in the male and lies under the breast in the female. Origin and insertion It arises from the anterior surface of the sternal half of the clavicle; from breadth of the half of the anterior surface of the sternum, as low down as the attachment of the cartilage of the sixth or seventh rib; from the cartilages of all the true ribs, with the exception, frequently, of the first or seventh and from the aponeurosis of the abdominal external oblique muscle. From this extensive origin the fibers converge toward their insertion; those arising from the clavicle pass obliquely downward and outwards (laterally), and are usually separated from the rest by a slight interval; those from the lower part of the sternum, and the cartilages of the lower true ribs, run upward and laterally, while the middle fibers pass horizontally. They all end in a flat tendon, about 5 cm in breadth, which is inserted into the crest of the greater tubercle of the humerus. Laminae This tendon consists of two laminae, placed one in front of the other, and usually blended together below. * The anterior lamina, which is thicker, receives the clavicular and the uppermost sternal fibers. They are inserted in the same order as that in which they arise: the most lateral of the clavicular fibers are inserted at the upper part of the anterior lamina; the uppermost sternal fibers pass down to the lower part of the lamina which extends as low as the tendon of the Deltoid and joins with it. * The posterior lamina of the tendon receives the attachment of the greater part of the sternal portion and the deep fibers, i. e., those from the costal cartilages. These deep fibers, and particularly those from the lower costal cartilages, ascend the higher, turning backward successively behind the superficial and upper ones, so that the tendon appears to be twisted. The posterior lamina reaches higher on the humerus than the anterior one, and from it an expansion is given off which covers the intertubercular groove of the humerus and blends with the capsule of the shoulder-joint. From the deepest fibers of this lamina at its insertion an expansion is given off which lines the intertubercular groove, while from the lower border of the tendon a third expansion passes downward to the fascia of the arm. Variations The more frequent variations include greater or less extent of attachment to the ribs and sternum, varying size of the abdominal part or its absence, greater or less extent of separation of sternocostal and clavicular parts, fusion of clavicular part with deltoid, and decussation in front of the sternum. Deficiency or absence of the sternocostal part is not uncommon. Absence of the clavicular part is less frequent. Rarely, the whole muscle is missing. This may accompany absence of the breast in females. (See Poland syndrome). Training The pectoralis muscle can be trained for athletic or bodybuilding purposesChest Exercise Menu. The following compound exercises are often used to increase the strength and mass of the muscle: *Bench press, with various bench angles (flat, incline, and decline) *Press up *Dips Isolation exercises include: *Flyes or Flies *Cable Crossovers * "Pec Deck" machines Additional images Image:Gray410.png|Superficial muscles of the chest and front of the arm. Image:Illu trunk muscles.jpg|Muscles of the trunk Image:Gray115.png|Anterior surface of sternum and costal cartilages. Image:Gray200.png|Left clavicle. Superior surface. Image:Gray201.png|Left clavicle. Inferior surface. Image:Gray207.png|Left humerus. Anterior view. Image:Gray523.png|The axillary artery and its branches. Image:Gray525.png|The brachial artery. Image:Gray558.png|The veins of the neck, viewed from in front. Image:Gray808.png|The right brachial plexus with its short branches, viewed from in front. Image:Gray809.png|The right brachial plexus (infraclavicular portion) in the axillary fossa; viewed from below and in front. Image:Nerves_of_the_left_upper_extremity.gif|Nerves of the left upper extremity. Image:Gray1215.png|The left side of the thorax. Image:Gray1219.png|Surface anatomy of the front of the thorax and abdomen. External links * * * * UCC Category:Muscles of the upper limb Notes * ar:عضلة صدرية كبيرة de:Musculus pectoralis major es:Pectoral mayor fr:Muscle grand pectoral hr:Veliki prsni mišić id:Otot pectoralis major it:Muscolo grande pettorale he:שריר החזה הגדול la:Musculus pectoralis maior hu:Nagy mellizom nl:Musculus pectoralis major ja:大胸筋 pl:Mięsień piersiowy większy pt:Músculo peitoral maior sk:Veľký prsný sval sl:Velika prsna mišica fi:Rintalihas sv:Stora bröstmuskeln zh:胸大肌